Cutting a solid surface to make a overlapping junction

This one is a bit tricky.

I'm building a RC submarine in Blender so that I can have it 3d printed. I want to have a removable "cap" so that I can have access to the electronics inside, however, to make it water tight, I want to put in a piece of rubber inside an overlapping junction. I know I can use the knife tool to cut out the cap and I solidified my sub to give it a "wall", however is there an easy way to cut an overlapping junction?

I also found that when I solidify, I can't seem to select the vertices on the expanded solid. Is this by design? Is there a way to enable it?

Normal Cut

XXXXXOOOOO
XXXXXOOOOO
XXXXXOOOOO


Side A

XXXXXXXXXX
XXXXX


Side B

     OOOOO
OOOOOOOOOO


Together

XXXXXXXXXX
XXXXXOOOOO
OOOOOOOOOO


Thanks,

mj

• You need to apply the solidify modifier first if you want to cut it like that (if I understood correctly) If you want to select the solidified vertices in edit mode, you can click on the downward facing triangle on the top row of the modifier header. But you won't be able to independently move a solidified vertex from its "base" counterpart until you apply the modifier. Jun 22 '20 at 12:46
• Do you need to leave a gap to accommodate your rubber gasket, or 'o' ring? Jun 22 '20 at 20:59

You could use a Boolean Modifier. Though, the success of this method may depend on the topology of your mesh. It does not always give clean or desired results, but it may be worth a try.

Also you will want Solidify to be above Boolean in your modifier stack. And if you apply these modifiers, apply the Solidify first, and then apply the Boolean.

EDIT:

You could make something like this, where the selected mesh is the (already applied) Boolean target object.

If you put the selected orange edge, shown on the left, (one is extruded inward, and one extruded outward) in in the middle of the solidified wall thickness, and then preform the boolean operation, you will end up with submarine parts that will fit into each other as shown on the right.

• It hit me last night to try that too. I added a pic of the model above. Since the sub is cylindrical, is it possible to create a quarter-cylinder where i expand the radius outward to cut the hole and another quarter-cylinder (more of a thick arc) that i pull back in to make the cut on one overlap edge?
– mj_
Jun 22 '20 at 15:55
• If i understand you correctly, then yes it is possible. I edited my answer accordingly, (If i didn't understand you correctly I suggest you try it and find out yourself) : ) Jun 22 '20 at 18:21
• @Fjoersteller .. my apologies, I seem to have DV'd this answer by accident, when I meant to UV it. If you make an edit to your answer, I can correct that. Jun 25 '20 at 20:33
• No apology needed. I mainly hope the answer is of some help to people (especially the one who asked it of course) But your diligence to be correct is appreciated, and i found a typo, so i will oblige. : ) Jun 25 '20 at 22:16